The present invention relates to electrometallurgical processes wherein the concentrated thermal energy of an electric arc is used for heating metal in melting furnaces. More specifically, it relates to a method of generating plasma in a plasma-arc torch and an arrangement in a plasma-arc torch used for heating metal.
For the purposes of the present invention by a plasma-arc torch is meant an apparatus adapted to generate a jet of "cold" plasma.
Plasma-arc torches generally comprise a water-cooled torch body having a nozzle, and a centrally positioned electrode made from a refractory metal, such as tungsten or molybdenum, with emissive additives. In transferred arc plasma-arc torches a plasma-generating gas, such as hydrogen, nitrogen, argon, helium and so on, turns to plasma in an arc discharge sustained between a refractory cathode and a workpiece serving as the anode.
In non-transferred plasma-arc torches plasma is generated between a cathode and an anode arranged as a constructed annular nozzle.